Nutrition’s Link to Sleep Quality
By Carrie Dennett, MPH, RDN
Today’s Dietitian
Vol. 25 No. 2 P. 34
What nutrients and foods play a role in getting some much-needed Zs?
As dietitians, many of your clients endure long workdays, take care of their children and families, and run weekly errands. But when their stressful day is done and it’s time to go to sleep, many find it difficult to unwind and rest and get the amount of sleep they need for optimal health.
The National Sleep Foundation defines adequate sleep as seven to nine hours per night for adults aged 26 to 64 and seven to eight hours per night for adults aged 65 and older.1 A joint consensus statement from the American Academy of Sleep Medicine and Sleep Research Society recommends seven or more hours of sleep per night on a regular basis to promote optimal health among adults aged 18 to 60.2 Unfortunately, most Americans don’t meet these recommendations.
Self-reported sleeping hours among US adults based on the National Health and Nutrition Examination Survey (NHANES) 2007–2010 show that an estimated 37.3% of US adults are getting six hours or less of sleep per night, with only 60.4% reporting that they get seven to nine hours of sleep per night.3 This may be due to intentionally skimping on sleep or caused by sleep disorders such as insomnia, sleep apnea, or circadian rhythm disorders.
A clear link exists between insufficient sleep—less than six hours for adults and five to six hours for older adults—and CVD and the development of inflammation in the body.1,4 Even short sleep—generally defined as getting less than seven hours of sleep per night—is associated with several disease-related biomarkers, including higher blood pressure, impaired glucose tolerance, higher triglycerides, lower HDL cholesterol, and inflammation. It’s also associated with all-cause mortality, likely because of the association with cardiometabolic risk factors.3 People who sleep for less than seven hours per day are at increased risk, with the greatest risk among those sleeping less than five hours per day.4
Because diet, in part, also affects cardiometabolic risk factors, there’s growing interest on the impact of sleep on diet and vice versa and their association with chronic disease risk.4 The processes that link sleep duration, sleep quality, and sleep behaviors to nutrition and chronic disease risk are complex. Current research suggests the relationship between sleep quality/duration and diet is bidirectional. Nutrition can have a significant impact on how we sleep, and how we sleep can affect our eating behavior. This means managing sleep is one way to improve nutrition, but improving nutrition may be a tool to improve sleep.5
Micronutrients and Short Sleep
An analysis of NHANES data from 26,211 participants found that adults with short sleep duration were more likely to have inadequate intakes from food and supplements of several micronutrients, including calcium, magnesium, and vitamins A, C, D, and E. While males were more likely than females to report short sleep, females had inadequate intakes of more of the nutrients associated with short sleep, as did adults aged 51 and older.3
• Calcium. While most calcium research is related to bone health, a 2014 study using NHANES data found that inadequate calcium intake was independently associated with difficulty falling asleep and nonrestorative sleep.6 Other research has found that calcium, together with magnesium and potassium, helps regulate the sleep/wake cycle and may play an important combined role in melatonin production. It’s also notable that chronic sleep deprivation negatively affects bone mass and bone metabolism.3 Good sources of calcium include dairy foods, calcium-fortified juices and plant-based milks, canned sardines and salmon (with bones), winter squash, tofu made with calcium sulfate, almonds, and leafy greens.
• Magnesium. Numerous studies have observed an association between magnesium deficiency or inadequate magnesium intake and very short sleep (five hours or less per night) and daytime sleepiness.3 A double-blinded placebo-controlled trial with elderly subjects found that taking 500 mg magnesium daily for eight weeks increased sleep time, sleep efficiency, and serum melatonin concentration, and decreased the Insomnia Severity Index score, sleep onset latency, and serum cortisol concentration compared with placebo.7 The specific mechanisms by which magnesium supports sleep aren’t fully understood, but studies have shown that magnesium plays essential roles in the sleep-wake cycles in the body. Daily magnesium fluxes are thought to regulate cellular timekeeping and energy balance. Magnesium has an indirect but essential role in facilitating the function of N-methyl-D-aspartic acid receptors, which is important for sleep regulation. Magnesium also may play a role in melatonin synthesis.3 In general, fiber-rich foods also provide magnesium, but specific food sources include green leafy vegetables, legumes, nuts, seeds, and whole grains. Magnesium also is added to some breakfast cereals and fortified foods.
• Vitamin D. Vitamin D receptors have been identified in regions of the brain that regulate sleep, and a 2018 systematic review and meta-analysis of nine studies involving 9,397 participants suggests that vitamin D deficiency is associated with a higher risk of sleep disorders, including poor sleep quality, short sleep duration, and daytime sleepiness.8 Vitamin D also may be involved in decreased release of inflammatory substances that play roles in sleep regulation.3 Fatty fish are the best dietary sources of vitamin D. Most fluid cow’s milk, as well as many plant-based milks, breakfast cereals, orange juices, and other food products, are fortified with some vitamin D.
• Vitamin C. Associations between low vitamin C intake and short sleep may be due to the fact that most dietary vitamin C comes from fruits and vegetables, low intake of which also has been linked to short sleep. Fruits and vegetables also contain an array of antioxidants, and it’s notable that smoking, which depletes blood levels of vitamins C and E as well as other antioxidants, also is associated with short sleep. There isn’t enough research looking at the effects of raising antioxidant status to know if it improves sleep duration.3 Citrus fruits and their juices, red and green peppers, and kiwifruit are the best sources of vitamin C.
• Vitamin A. Inadequate intake of vitamin A is associated with short sleep in adults of all ages. In the eye, vitamin A and pro-vitamin A carotenoids contribute to the sensing of light, which is important for synchronization of circadian rhythms.3 Vitamin A or pro-vitamin A carotenoids are found naturally in many foods, including fatty fish, eggs, green leafy vegetables, and other green, orange, and yellow vegetables, and some fruits, especially mango, cantaloupe, and pink or red grapefruit. Milk and dairy products, and many breakfast cereals, also are fortified with vitamin A.
• Omega-3 fatty acids. Eating fatty fish, such as salmon, mackerel, and trout, has a positive effect on sleep regulation. Fatty fish are a good source of omega-3s and vitamin D. These nutrients may influence the regulation of serotonin secretion and, thus, the regulation of sleep. Diets low in omega-3s may impair sleep by disturbing circadian rhythms and reducing melatonin secretion.4
Ikonte and colleagues emphasized that there are other micronutrients that appear to play a role in sleep and circadian regulation, including those that support melatonin synthesis (ie, folate, vitamin B6, zinc).3 And while average intake across the US adult population may be high enough to show up as nonsignificant associations in retrospective studies, some individuals may have deficits in these nutrients that impair normal sleep regulation.
Macronutrients, Eating Patterns, and Sleep Quality
Sleep also is influenced by the macronutrient content of the diet. Insufficient protein intake may impair sleep quality, while too much protein intake may lead to difficulties in maintaining sleep. High consumption of refined, high-glycemic carbohydrate foods, as well as the omission of breakfast and irregular meals, are associated with poor sleep, while a diet rich in fish, seafood, and vegetables contributes to good sleep.9 Eating foods high in the amino acid tryptophan, as well as melatonin and serotonin, improves sleep quality. Researchers have observed a longer downtime, increased performance, and improved total sleep time in adults after consuming foods rich in tryptophan.10
“The trend in cutting out carbohydrate foods, specifically high-quality carbohydrates like fruit and whole grains, is concerning to me, especially as it relates to sleep,” says Karman Meyer, RDN, author of Eat to Sleep: What to Eat & When to Eat It for a Good Night’s Sleep and The Everything DASH Diet Meal Prep Cookbook. “These foods often contain vitamin B6, which is involved in more than 150 enzyme reactions in the body, including the production of serotonin, which is often thought of as the ‘happy neurotransmitter.’” A deficiency in vitamin B6 can negatively affect mood, possibly contributing to depression, anxiety, and increased feelings of pain, all of which can interfere with sleep. If that’s not reason enough to enjoy more vitamin B6, it’s also essential in the making of melatonin, the sleep-promoting hormone.”
Results of a 2022 study using multinight in-home monitoring suggest that about 20% of adults have moderate-to-severe obstructive sleep apnea (OSA) and that about 20% of people diagnosed based on a single-night study may be misclassified.11 While weight loss often is “prescribed” for sleep apnea, results published last year from the INTERAPNEA randomized clinical trial in Spain found that an anti-inflammatory diet and lifestyle improvements improved severity of sleep apnea even when weight loss didn’t also occur.12 The intervention group was counseled to eat more healthful whole foods and avoid ultraprocessed foods, processed meats, salty snacks, and sugar-sweetened beverages. They also were asked to reduce nightly alcohol consumption, stop smoking, and increase daily step count.12 Results of the MIMOSA randomized clinical trial published in 2021 showed that men and women with moderate to severe OSA and BMIs in the “overweight” range improved their sleep apnea and experienced less insomnia and daytime sleepiness by following a Mediterranean diet rich in fish, whole grains, plants, and foods high in unsaturated fats. These outcomes occurred regardless of whether the participants lost weight.13
Looking at observational research, 2022 results of an analysis of data from the Nurses’ Health Studies I and II and the Health Professionals Follow-Up Study found that a more healthful diet, particularly one with anti-inflammatory potential, was associated with a lower OSA risk.14 A 2022 analysis of NHANES data also found that higher-quality and anti-inflammatory diets and a more healthful overall lifestyle was associated with lower sleep apnea risk.15
Caffeine and Alcohol
One element of a sleep-friendly diet that tends to elude people is what they drink, says Dana Angelo White, MS, RD, ATC, a Connecticut-based cookbook author, certified athletic trainer, and nutrition and fitness consultant. “Caffeinated beverages in the afternoon can inhibit your ability to enter those deep, restorative phases of sleep, even if you’re the type of person that can fall asleep with caffeine on board,” she says. “On the other end of the spectrum from stimulants, alcohol cocktails don’t help facilitate sleep. The sedative effect of alcohol wears off and will wake you up again, disrupting those precious sleep cycles.”
An increase in the number of people who sleep for less than six hours per night is influencing caffeine consumption. Caffeine increases performance, but it also affects the quality of sleep, setting up a vicious cycle. People who consume large amounts of caffeine are more likely to be drowsy in the morning compared with those who consume moderate amounts.16
“The effect caffeine has on sleep is related more to the timing of consumption rather than the overall quantity consumed during the day,” Meyer says. “The recommended limit for daily caffeine intake is 400 mg, which is about four 8-oz cups of brewed coffee, so it’s best not to exceed that.” She emphasizes that some people are affected by caffeine intake more strongly than others due to having less of the liver enzyme that processes caffeine. Therefore, it’s important for clients and patients to pay attention to how caffeine makes them feel. “General recommendations are to cut off caffeine intake eight to 10 hours before your usual bedtime, so if you want to get to sleep by 10 pm, cut off the caffeine by 2 pm.”
White goes further than that, recommending stopping caffeine consumption at noon. “It’s unpopular, but it makes sense if you do the math. The half-life of caffeine is four to six hours, so cutting it off by noon (or earlier) is the best way to help ensure most of it is out of your system when it’s time to sleep.”
Meals and Snacks for Better Sleep
So, what foods, or combination of foods, can dietitians recommend to clients and patients who want to sleep longer and more soundly?
“One of the foods I consistently recommend for better sleep is tart cherry juice since it’s a natural source of melatonin and has been studied for its sleep benefits,” Meyer says. “Drinking 8 oz of tart cherry juice in the morning and then one to two hours before bedtime was found to extend sleep duration by 84 minutes in a group of individuals suffering from insomnia. This is often a very simple addition that people can add to their day to get better sleep.”
Oatmeal cooked in milk with dried tart cherries, nuts, and sliced bananas is one idea to bring together an array of sleep-friendly nutrients. Scrambled eggs with spinach, tomatoes, and avocado have similar sleep benefits. Grilled chicken on a green salad topped with colorful vegetables, nuts, and cooked whole grains—or rolled into a whole grain wrap—paired with fruit for dessert will carry the sleep-supportive benefits into lunch. Dinnertime is a great time to get a boost of omega-3s with salmon or other fatty fish, paired with brown rice or other whole grains—perhaps in pilaf form with chopped nuts and a colorful side of cooked veggies or a raw vegetable salad.
Many people have food rules about not eating later in the evening, but a properly constructed evening snack can aid sleep. “A well-balanced snack that includes protein, fat, and fiber can be a beneficial addition to the evening routine, especially if you eat dinner four to five hours before going to bed,” Meyer says. “A small evening snack can prevent you from waking up hungry in the middle of the night and reduce the risk of blood sugar dropping, which leads to a release of adrenaline and cortisol that will wake you up. Choose something like a banana with nut butter, cottage cheese and fruit, a few cheese cubes with whole wheat crackers, or almonds paired with dried tart cherries.”
White says calcium and potassium are big winners for evening snacks. “Calcium helps the body make melatonin, and potassium helps blood flow and muscles relax,” she says. “A rice cake with peanut butter and banana with a glass of milk is one of my favorite bedtime snacks.” Overall, White says a combination of sensibly portioned carbs and protein is the winning combination for a healthful and satisfying bedtime snack.
Whether the last eating episode of the day is dinner or a snack, size and timing are key, White says. “Eating a large meal too close to bedtime can be disruptive to sleep, so I suggest giving it at least an hour or two before lying down.”
— Carrie Dennett, MPH, RDN, is the nutrition columnist for The Seattle Times, owner of Nutrition By Carrie, and author of Healthy for Your Life: A Holistic Guide to Optimal Wellness.
References
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